Concrete mixing apparatus



y 1957 MAXON, JR 2,801,085

CONCRETE MIXING APPARATUS Filed June 20, 1955 3 Sheets-Sheet l Flazzwy Max:722 .5:

July 30, 19 G. MAXON, JR

CONCRETE MIXING APPARATUS 5 heets-Sheet 2 Filed June 20, 1.955

y 1957 e. MAXON, JR 2,801,085

CONCRE'IVE MIXING APPARATUS Filed June 20, 1955 '5 sheets-S ea 5 5/): w; y Mama J2:

United States atent CONCRETE MIXING APPARATUS Glenway Maxon, Jr., Milwaukee, Wis.

Application June 20, 1955, Serial No. 516,716

6 Claims. ((31. 259171) This invention relates generally to improvements in concrete mixing apparatus such as that disclosed in Patent No. 2,590,438, issued to Glenway Maxon, Jr., on March 25, 1952. More particularly, this invention refers to mixing apparatus of the type having a rotatable mixing drum which is tiltably supported at an elevation above ground level for discharge of its contents directly into the body of a transit truck.

Heretofore mixing apparatus of this type was invariably provided with a mixing drum rotatably mounted in a cradle transversely embracing a medial portion of the drum and the cradle, in turn was pivotally mounted on a stationary U-shaped subframe for rotational motion about a fixed axis to tilt the drum thereon forwardly from mixing to discharging positions and thus efiect discharge of the drum contents through an opening in the forward axial end of the drum.

My aforesaid patent teaches the desirability of locating the tilt axis close to the discharge end of the drum so that virtually the entire weight of the drum and its contents is concentrated at a location rearwardly of the tilt axis in both the mixing and the discharging positions of the drum. With this location of the tilt axis, the drum returns to its mixing position by gravity and single acting hydraulic cylinders may be used to tilt the cradle and drum out of mixing position. Such location of the tilt axis close to the discharge end of the drum also assures controlled pouring of the drum contents when the drum is tilted to its discharge position, and this feature is highly important for the reason that it enables the drum to be mounted at a minimum elevation above ground level for discharge directly into the body of a transit truck.

In general, it is the object of this invention to provide concrete mixing apparatus which features an improved manner of effecting tilting of the cradle and the drum thereon, not about a fixed axis as was always the case heretofore, but through the provision of cooperating rocker elements carried by the cradle and its supporting structure and upon which the cradle may roll bodily back and forth to eifect tilting of the drum thereon to and from a discharging position at which the discharge end of the drum is lowermost.

it is also a purpose of this invention to provide concrete mixing apparatus of the character described which achieves all of the advantages of my aforesaid patent, but which has the additional feature of enabling the subframe previously used to support the cradle to be eliminated entirely. This provides more clearance for the body of a transit truck beneath the discharge end of the mixing drum, and generally simplifies the construction and erection of so-called portable mixing plants of the type which are adapted to be moved from one location to another on larger road building jobs and the like.

With the above and other objects in view, which will appear as the description proceeds, this invention resides ice in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure l is a side elevational view of mixing apparatus embodying the principles of this invention, the apparatus being mounted on an easily moved supporting structure with the mixing drum arranged to discharge directly into the body of a transit truck;

Figure 2 is a side elevational view of the mixing apparatus seen in Figure 1, but showing the mixing drum tilted to its discharging position; and

Figure 3 is a front elevational view of the mixing apparatus shown in Figure 1.

Referring now more particularly to the accompanying drawings in which like numerals indicate like parts, the numeral 5 generally designates the mixing apparatus of this invention which, by way of illustration, is shown supported by and between a pair of upright columns 6 formin part of an easily erected and dismantled supporting structure of a type which may be quickly moved from place to place. The apparatus includes a rotatable mixing drum 7 having a frustoconical forward section 8, a similar frustoconical rear section 9, and a substantially cylindrical medial section 10, the ends of which are joined to the large diameter ends of the front and rear frustoconical sections 8 and 9.

As is customary, the mixing drum is provided with a discharge opening 12 in its forward axial end and the rear end of the drum may also have an opening 13 therein coaxial with the opening 12 through which materials to be mixed may be charged into the drum.

The drum 7 is rotatably mounted in a substantially crescent or U-shaped cradle 15 of a more or less conventional type and which passes under and embraces the cylindrical medial section 10 of the drum to have the extremities of its upwardly extending legs 16 disposed close to the wall of the drum at opposite sides thereof. Following more or less conventional practice, the mixing drum is mounted for and constrained to rotation on the cradle by means of a ring or flange 18 fixed on the cylindrical side wall section 14) of the drum and tracking on a pair of relatively large rollers 19 journaled on the lower closed end of the cradle, the flange being embraced by a plurality of pairs of auxiliary rollers 24 also carried by the cradle. The ring gear 21 by which the drum is adapted to be rotated, encircles and is fixed to the ring 18.

With the construction described, the rollers 19 and 20 cooperate to constrain the drum to rotate on an axis fixed with respect to the cradle, and such rotation may be imparted to the drum as by means of an electric motor 23 carried by one of the legs 16 of the cradle and drivingly connected with the ring gear through a drive pinion 24.

The cradle 15 and the mixing drum carried thereby are mounted upon the supporting structure with the drum between the upright columns and the extremity of each of the legs 16 of the cradle adjacent to one of the columns. For this purpose, the supporting structure includes a pair of arms 26 joined to the upright columns 6 and projecting forwardly and at a slight upward inclination from the plane containing the columns. Each end portion 16 of the cradle has an arcuate rocker 27 fixed thereto and resting upon the arms 26 to mount the cradle and the drum thereon upon the supporting structure for bodily back and In the mixing position of the drum seen inFigure 1, the lower end portions of the arcuate rockers seat upon the inner end portions of the arms 26, while the outer end portions of the rockers recede from the upper faces of the arms. Also in the mixing position seen in Figure 1,

the opposite legs 16 of the cradle extend substantially vertically upwardly in the plane containing the columns 6, and this position of the'cradle and the drum carried thereby is defined by the engagement of abutments 29 .on the rear endsfof the rockers with upstanding abutments 30 on the arms 26 adjacent to their inner ends.

a If desired, a pad 31 of rubber or other resilient materialmay be interposed between the abutments 29 and 30 to cushion the return of the drum to its mixing position from the tilted discharging position thereof seen in Figure 2.

A characteristic feature of the construction described thusrfar is that the drum is tilted back and forth between mixing and discharging positions without entailing pivotal motion of the cradle about a fixed axis, as was the case in all past mixing apparatus of the type herein concerned. Such tilting of the drum is effected solely as a consequence of bodily back and forth rolling of the cradle on its rockers 27 along the upper surfaces of the arms 26. To assure against slippage of the rockers on the arms, meshing gear teeth 33 may be provided on their opposing faces in the manner shown; although other expedients such as crossing chains or cables connected between the cooperating rocker elements will readily suggest themselves.

While the rockers 27 on the cradle have been shown provided with downwardly facing convex surfaces and the arms 26 as being generally straight with a slight upward and forward inclination, it will be appreciated that, alternatively, the rockers 27 may be straight while the arms 26 maybe convexly curved. It is advantageous, however, to employ the construction disclosed in the drawings for the reason that it minimizes lowering of the discharge end portion of the drum as it is tilted toward its discharging position. 7

Due to the disposition of the rockers with respect to the cradle and the drum carried thereby, the center of gravity of the combined structure, including the drum contents; will always be disposed rearwardly of the areas of engagement between the rockers 27 and the arms 26 upon which they track, regardless of whether the drum is in its mixing position, seen in Figure l, or in its extreme discharging position, seen in Figure Z. This is an important feature of the invention by reason of the fact that gravity can be relied upon to return the drum to its mixing position.

Hence, single acting hydraulic cylinders35, one at each side of the drum and mounted on the supporting structure, may be used to effect bodily forward rolling of the cradle and the drum thereon to the discharging position. When the fluid pressure in the cylinders is relieved by suitable valve mechanism, not shown, the weight of the drum effects retraction of the cylinder and return of the drum to its mixing position.

The hydraulic cylinders 35 may be of any suitable type, but are shown as comprising a body 36 pivotally supported as at 37 on rearward extensions of the arms 26 and having extensible rams 38 pivotally connecting with upstanding lever arms 39 fixed on the'rear end portions of the rockers 27, In the mixing position of the cradle and drum shown' in Figure 1, the cylinders are disposed the front or discharge end of the drum.

One of the main features'of the construction described is that the rocker-mounting of the cradle on the supporting structure eliminates the need for a subframe of the type conventionally employed to pivotally support the cradle. A subframe of the type referred to is disclosed in my aforesaid Patent No. 2,590,438 and is mounted on the supporting structure ahead of the cradle and the supporting columns, with its intermediate portion under the drum and extremely close to the discharge end of the drum when the latter is tilted to its discharging position. With the patented structure referred to, therefore, the subframe limits the extent to which transit trucks or other conveyances may be run under the forward end of the drum to have the contents thereof discharge directly into the truck body.

With the present invention, however, the elimination of the subframe makes it possible to position the body of a dump truck or other transit vehicle closely adjacent to the plane containing the supporting columns. 6 to better receive the concrete discharged from the drum.

It is also highly important to note that, since the rockers 27 mount the cradle for bodily back and forth rolling motion along the arms 26, a highly desirable tilting motion is imparted to the mixing drum. The drum does not tilt about a fixed axis during the power stroke of the hydraulic cylinders 35 but, instead, every point on the drum spaced from the axis of the rocker-s 27' travels in a cycloidal path, and the drum is moved bodily forwardly and upwardly to its discharging position. Since there is aminirnum amount of lowering of the forward discharge end portion of the drum during such tilting motion thereof, and. the rear end portion of the drum is lifted a substantial amount, there is no tendency for the drum contents to be spewed out in an uncontrolled fashion which would requirethe use of collecting hoppers or chutes to receive and direct the contents of the drum into the truck body. The discharge of material from the drum is, therefore, characterized by a smooth pouring action which is controlled at all times. a

From the foregoing description taken together with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention materially simplifies concrete mixing apparatus of the type which is especially suited for portable mixing or batching plants, by the elimination of the subframe commonly provided in the past to pivotally support the cradle and drum; and that the elimination of the subframe is made possible through the use of cooperating rocker. elements on the cradle and the supporting structure therefor to support the cradle for the bodily back and forthrolling motion necessary to tilt the drum between mixing and discharging positions.

What I claim as my invention is:

l. in concrete mixing apparatus of the type having a rotatable mixing drum provided with a discharge opening in its forward axial end, and having a cradle in which the drum is rotatably mounted with the opposite ends of the cradle lying at opposite sides of the. drum: a supporting structure comprising a pair of upright supports, one adjacent to each end of the cradle; a pair of upwardly inclined arms on said supporting structure projecting forwardly from the plane containing said 'supports; an arcuate rocker element on each end portion of the cradle, said rocker elements resting on said in clined arms to mount the cradle on the supporting structure with the discharge end of the drum facing forwardly, and providing for forward and upward bodily rolling motion of the cradle along the arms to tilt the drum from a mixing position toward a discharging position at which the discharge end of the drum is lowermost; and power operated means carried by the supporting structure and connected with the cradle for rolling the cradle bodily forwardly along the upwardly inclined arnis to effect tilting o'fthe drum to the discharging position thereof.

2L.In concrete mixing apparatus of the type having,

ing in its forward axial end, and having a cradle in which the drum is rotatably mounted with the opposite ends of the cradle lying at opposite sides of the drum: a pair of upright supports, one adjacent to each end of the cradle; means movably mounting the cradle on said supports to provide for tilting of the drum from a mixing position to a discharging position at which the forward axial end of the drum is lowermost, said means comprising arcuate rocker elements fixed on the cradle at each side of the drum and extending generally lengthwise of the axis of the drum, and cooperating arms fixed on said supports and upon which said rocker elements track to provide for back and forth bodily rolling motion of the cradle and the drum thereon along a path substantially normal to the plane containing said upright supports; cooperating abutments on the supports and the cradle to limit rearward rolling motion of the cradle and thus define the mixing position of the cradle and the drum thereon; and power operated means connected between said supports and the cradle for imparting forward rolling motion to the cradle and the drum thereon in the direction to eifect tilting of the drum to its discharging position.

3. The concrete mixing apparatus set forth in claim 2 further characterized by the fact that said rocker elements are located generally below the axis of rotation of the drum and alongside the front end portion of the drum so that the rear portions of the drum are lifted upwardly upon forward rolling of the cradle in the direction to tilt the drum toward its discharging position; and further characterized by the fact that said power operated means comprises a single acting hydraulic cylinder positioned to be retracted by the tendency of the drum and cradle to return to mixing position by gravity.

4. In concrete mixing apparatus of the type having a rotatable mixing drum provided with a discharge opening in its forward axial end, and having a cradle in which the drum is rotatably mounted with the opposite ends of the cradle lying at opposite sides of a medial portion of the drum and an intermediate portion of the cradle extending transversely across the exterior of the drum; a stationary structure; and means mounting the cradle and the drum thereon upon said stationary structure for bodily back and forth motion in unison between a normal mixing position and a discharging'position at which the discharge end of the drum is lowermost, said means comprising cooperating supports on the cradle and on said stationary structure, said supports extending forwardly away from the cradle toward the discharge end of the drum from locations adjacent to the cradle and having vertically opposed surfaces adapted for supporting engagement with one another, one of said supporting surfaces being curved and diverging from the opposing supporting surface toward the outer ends of said supports, whereby the latter mount the cradle and drum thereon for forward bodily rolling motion in unison between a normal mixing position at which surface areas at the inner portions of said supports have supporting engagement with one another, toward a discharging position at which surface areas near the outer portions of said supports have supporting engagement with one another, said areas of supporting engagement between the opposing surfaces on said supports moving progressively forwardly relative to the drum as tilting progresses so that said areas of supporting engagement Will at all times lie ahead of a vertical plane passing transversely through the center of gravity of the drum.

5. As an article of manufacture: a rigid substantially U-shaped cradle having opposite upwardly extending legs adapted to embrace the opposite sides of a mixing drum, and having a bight portion extending transversely between the lower portions of said legs and adapted to lie beneath a medial portion of a mixing drum in position between the cradle legs; means on the cradle adapted for engagement with annular portions of a drum embraced by the cradle to constrain the drum to rotation on an axis fixed with respect to the cradle, and transversely spaced opposite rockers joined to the cradle and projecting wholly to one side of the plane of the cradle legs, said rockers curving outwardly and upwardly away from the cradle and having downwardly facing substantially convex supporting surfaces thereon providing for supporting the cradle for back and forth rolling motion between a normally upright position at which the cradle is supported by surface areas at the inner portions of the rockers, and a tilted position at which the cradle is sup ported by surface areas at the outer portions of the rockers, and at which tilted position the cradle legs extend over the rockers.

6. The article of manufacture set forth in claim 5 further characterized by the fact that said rockers are joined to the cradle legs at areas remote from the bight portion of the cradle, and wherein the rockers are curved outwardly and upwardly away from the cradle legs and have their extremities disposed at a level adjacent to that of the cradle legs when the cradle is in said normally upright position.

References Cited in the file of this patent UNITED STATES PATENTS 

